Embodiments of the present invention generally relate to a method for detecting wireless communication packets that use a coded sequence, e.g., a preamble sequence to aid detection. In wireless communications, packets of information are transmitted and received. A preamble sequence is placed within the transmitted packet so that a receiver will be able to recognize the preamble sequence and perceive that a packet has been received. A typical transmitted preamble sequence may be given asp[k]=[p1, p2, p3, . . . , pk−1, pk].  (EQU. 1)
There are a number of means for encoding a preamble sequence and detecting the preamble sequence at the receiver side. One is called coherent integration. The other is called non-coherent integration. In coherent integration, a filter is applied where every single tap of the filter matches every single element of the preamble sequence. This technique provides very good gain but is subject to performance degradation in the presence of Doppler shifts and dynamic multipath. An example of a matched filter may be given ash[k]=[pk*, pk−1*, . . . , p3*, p2*, p1*].  (EQU. 2)
When there exists a frequency offset in the received signal after conversion to a frequency appropriate for correlation processing, or when the channel amplitude and phase characteristics vary over the time period of the preamble, the detection filter is no longer matched so that there is a significant signal-to-noise ratio (SNR) loss. To address this SNR loss, current methods include separating the preamble sequence into segments or subsymbols, where ideal matched filtering is performed on one or more segments and the resulting real magnitudes or squares of magnitudes are added together. The use of ideal matched filtering on segments of the preamble is known as non-coherent integration. However, non-coherent integration suffers from processing loss relative to an ideal matched filter.
Therefore, there is a need in the art for a wireless communications packet detection and/or synchronization method that is resistant to degradation caused by frequency shifts and is resistant to degradation caused by limited channel coherency.